fn1()
function  fn1(){
    const xhr = new XMLHttpRequest();
    xhr.open('POST', '/users/login', true);
    xhr.onload = function () {
        const res = JSON.parse(xhr.responseText);
        console.log(res);
    }

    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xhr.send('username=panpan&password=123321');
}